arXiv subjects

Jack W. Sulentic

Publications and source records attributed to Jack W. Sulentic.

22 records · Page 2Linked to original sources

arXiv2000

The Demise of the Classical BLR in the Luminous Quasar PG1416-129

New observations of the broad-line quasar PG1416-129 reveal a large decline in its continuum luminosity over the past ten years. In response to the continuum change the ``classical'' broad component of Hbeta has almost completely disappeared (a x10 decrease in flux). In its place there remains a redshifted/redward asymmetric very broad emission line component. The significance of this change is multifold: (1) It confirms the existence of a distinct redshifted Very Broad Line Region (VBLR) component that persists after the demise of the broad component and that is frequently observed, along with the broad component, in radio-loud sources. (2) The smaller (x2) intensity change in the Hbeta very broad component supports the previously advanced idea that the VBLR is physically distinct and likely to arise in an optically thin region close to the central source. (3) The presence of a strong very broad component in the radio-quiet quasar PG1416-129 reinforces the notion that such ``population B'' quasars share similar spectroscopic (and hence geometrical and kinematical) properties to radio-loud sources. (4) AGN can show broad, very broad, or both line components simultaneously, making statistical comparisons of source profile widths difficult. (5) The interpretation, in reverberation studies, of the presence or lack of correlated response in broad line wings will be affected by this composite BLR/VBLR structure.

astro-ph↗

arXiv2000

Mapping IR Enhancements in Closely Interacting Spiral-Spiral Pairs. I. ISO~CAM and ISO~SWS Observations

Mid-infrared (MIR) imaging and spectroscopic observations are presented for a well defined sample of eight closely interacting (CLO) pairs of spiral galaxies that have overlapping disks and show enhanced far-infrared (FIR) emission. The goal is to study the star formation distribution in CLO pairs, with special emphasis on the role of 'overlap starbursts'. Observations were made with the Infrared Space Observatory (ISO) using the CAM and SWS instruments. The ISO~CAM maps, tracing the MIR emission of warm dust heated by young massive stars, are compared to new ground based H$α$ and R-band images. We identify three possible subgroups in the sample, classified according to the star formation morphology: (1) advanced mergers (Arp~157, Arp~244 and Arp~299), (2) severely disturbed systems (Arp~81 and Arp~278), and (3) less disturbed systems (Arp~276, KPG 347 and KPG 426). Localized starbursts are detected in the overlap regions in all five pairs of subgroups (1) and (2), suggesting that they are a common property in colliding systems. Except for Arp~244, the 'overlap starburst' is usually fainter than the major nuclear starburst in CLO pairs. Star formation in 'less disturbed systems' is often distributed throughout the disks of both galaxies with no 'overlap starburst' detected in any of them. These systems also show less enhanced FIR emission, suggesting that they are in an earlier interaction stage than pairs of the other two subgroups where the direct disk collisions have probably not yet occurred.

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arXiv1998

The Observational Status of Stephan's Quintet

We present new photometric and spectroscopic data for the galaxies in the compact group known as Stephan's Quintet. We find the strongest evidence for dynamical perturbation in the spiral component NGC7319. Most of the damage was apparently caused by nearby NGC 7320C which passed through the group a few times 10(^8) years ago. NGC7318B is a spiral galaxy that shows evidence consistent with being in the early stages of a collision with the group. NGC7317 and 18A are either elliptical galaxies or the stripped bulges of former spiral components. They show no evidence of past or present merger activity but are embedded in a luminous halo which suggests that they are interacting with the other members of the group. The low redshift galaxy NGC7320 is most likely a late type, dwarf spiral projected along the same line of sight as the interacting quartet.

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arXiv1992

Evidence for a Very Broad Line Region in PG 1138+222

We present a high S/N spectrum for the quasar PG 1138+222. We detect a very broad HeII$λ$4686 emission line component with twice the FWHM of the conventional broad line region (BLR) as evidenced by the Balmer lines. The profile shape and centroid redshift also distinguish this HeII component from the BLR features. The large ratio of HeIIł4686 to any analogous H$β$ emission component is an indicator that it arises in a very high density region ($n_e \simgt 10^{11}-10^{13}$ \cm3). This Helium component is probably emitted in a Very Broad Line Region (VBLR), where the radiation field is so strong that the Strömgren depth becomes similar to the geometrical thickness of the emitting clouds. The gas could therefore be optically thin to the Lyman continuum.

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